CHEM 233 Unit 1 Thin-Layer
Chromatography, Mass Spec and IR
Spectroscopy, NMR Spectroscopy Part
1: 1H NMR Question and answers
correctly solved 2025
Common Sense Question: It is possible to know what is in an unlabeled test
tube containing a clear and colorless solution by visually observing it. (1 pt) -
correct answer ✔False
Is it acceptable to mark the baseline (the starting line 1 cm from the plate
bottom) using a pen? (1 pt) - correct answer ✔No, because the ink will elute
up the plate and potentially obscure important data.
Switching from a less polar eluent to a more polar eluent using a normal
phase TLC plate will have what consequence? (1 pt) - correct answer
✔Increasing the polarity of the eluent causes all compounds to elute a longer
distance.
Select all of the following compounds that are not considered highly polar, that
is they do not form hydrogen bonding interactions. (1 pt) - correct answer
✔alkenes, alkanes, ethers
You develop and visualize a TLC with two lanes. The compound in lane 1
eluted a distance of 3.0 cm. The compound in lane 2 eluted a distance of 6.0
cm. The solvent front eluted a distance of 12.0 cm. Calculate the retention
factor of the compound in lane 1 to the hundredths place. (1 pt) - correct
answer ✔0.25
, You wish to analyze the purity of a compound via TLC. If you wanted polar
compounds to remain near the bottom (baseline) of the plate, what kind of
TLC plate would you use? (1 pt) - correct answer ✔A normal phase TLC
plate because the polar stationary phase will interact with polar compounds
more strongly.
You decide to use a plastic-backed TLC plate coated in silica gel. Which of
the following choices is the stationary phase? (1 pt) - correct answer ✔The
silica gel on the TLC plate
You are deciding which solvents to use to develop your TLC plate. Order the
following solvents from most polar to least polar where 1 is most polar and 3 is
least polar. (2 pt) - correct answer ✔1. isopropanol
2. acetone
3. toluene
You develop and visualize a silica gel TLC plate and are not satisfied with the
results. Which of the following experimental parameters would result in a
change in retention factors if you were to modify them in a properly performed
TLC analysis? Mark all that apply. (2 pt) - correct answer ✔changing the TLC
plate stationary phase
changing the solvent system polarity
You developed the silica gel TLC plate using 100% ethyl acetate. Which of the
following solvent systems would result in higher retention factors if you were
to analyze the sample via TLC the same way again? The structures of ethyl
acetate, ethanol, and hexane are shown below. (2 pt) - correct answer ✔50%
ethanol/50% ethyl acetate
100% ethanol
Chromatography, Mass Spec and IR
Spectroscopy, NMR Spectroscopy Part
1: 1H NMR Question and answers
correctly solved 2025
Common Sense Question: It is possible to know what is in an unlabeled test
tube containing a clear and colorless solution by visually observing it. (1 pt) -
correct answer ✔False
Is it acceptable to mark the baseline (the starting line 1 cm from the plate
bottom) using a pen? (1 pt) - correct answer ✔No, because the ink will elute
up the plate and potentially obscure important data.
Switching from a less polar eluent to a more polar eluent using a normal
phase TLC plate will have what consequence? (1 pt) - correct answer
✔Increasing the polarity of the eluent causes all compounds to elute a longer
distance.
Select all of the following compounds that are not considered highly polar, that
is they do not form hydrogen bonding interactions. (1 pt) - correct answer
✔alkenes, alkanes, ethers
You develop and visualize a TLC with two lanes. The compound in lane 1
eluted a distance of 3.0 cm. The compound in lane 2 eluted a distance of 6.0
cm. The solvent front eluted a distance of 12.0 cm. Calculate the retention
factor of the compound in lane 1 to the hundredths place. (1 pt) - correct
answer ✔0.25
, You wish to analyze the purity of a compound via TLC. If you wanted polar
compounds to remain near the bottom (baseline) of the plate, what kind of
TLC plate would you use? (1 pt) - correct answer ✔A normal phase TLC
plate because the polar stationary phase will interact with polar compounds
more strongly.
You decide to use a plastic-backed TLC plate coated in silica gel. Which of
the following choices is the stationary phase? (1 pt) - correct answer ✔The
silica gel on the TLC plate
You are deciding which solvents to use to develop your TLC plate. Order the
following solvents from most polar to least polar where 1 is most polar and 3 is
least polar. (2 pt) - correct answer ✔1. isopropanol
2. acetone
3. toluene
You develop and visualize a silica gel TLC plate and are not satisfied with the
results. Which of the following experimental parameters would result in a
change in retention factors if you were to modify them in a properly performed
TLC analysis? Mark all that apply. (2 pt) - correct answer ✔changing the TLC
plate stationary phase
changing the solvent system polarity
You developed the silica gel TLC plate using 100% ethyl acetate. Which of the
following solvent systems would result in higher retention factors if you were
to analyze the sample via TLC the same way again? The structures of ethyl
acetate, ethanol, and hexane are shown below. (2 pt) - correct answer ✔50%
ethanol/50% ethyl acetate
100% ethanol
